Spoiler: Did not build from scratch, used keycaps and keyboard switches.
Switching from keycaps to some substitute wouldn't be technically harder to pull off, it would just reduce usability. Same for switches -- the input/output of these switches is created with keyboards in mind, other switch choices including a homemade version would be possible, but he didn't set out to create 100 switches, he wanted to make a keyboard.
Looks like the author had fun, though.
This. Is. Bullocks!